Hot flushes pose a significant public health concern world-wide. These perimenopausal symptoms are the primary reason that women seek medical care during the menopausal transition. Hot flushes often negatively impact the quality of life of women because they are associated with anxiety/depression and sleep disturbances resulting in fatigue, irritability, and forgetfulness, as well as acute physical discomfort and negative effects on work. Although estrogen replacement therapy (ERT) is efficacious in preventing hot flushes, a large number of women cannot or do not want to take estrogen, and the peripheral side-effects are potentially life threatening. The efficacy of the other therapies is questionable. Therefore, there is a huge unmet need for a better and safer ERT We propose in this application that para-quinol of 17b-estradiol (Q-E2) has the potential to be considered as the optimal ERT. We have shown earlier that Q-E2 functions as a pro-drug and following its absorption it is converted in selective tissues to E2 via an enzyme catalyzed mechanism. This conversion is effective in the brain but not in the uterus, breast, or the pituitary gland. Therefore, treatment with Q-E2 would not have uterotropic and mammotropic liabilities like any other estrogens. Since E2 is the primary and most potent estrogen produced by the human ovary, we propose to consider Q-E2 as a pro-drug for the treatment of perimenopausal symptoms including not only hot flushes as we proposed in the parent grant but anxiety/depression and altered sleep pattern by utilizing animal models of these menopausal disturbances. Our pilot data strongly indicate that Q-E2 blocks hot flush symptoms in a rat model of hot flush, reduces depression in the forced swim test model of behavioral despair, but does not stimulate proliferation in MCF-7 breast cells or the uterus at doses that block the hot flush symptoms. Therefore, Q-E2 seems to be a novel, safe, and optimal ERT for alleviating perimenopausal symptoms, including hot flushes, anxiety/depression and sleep disturbances. The supplement describes a series of experiments aimed at evaluating the effect of orally-administered Q-E2 in (i) rat and mouse models of anxiety/depression and (ii) rat and mouse models of estrogen-regulated sleep patterns. Since the development of estrogen receptor-alpha (ERa)- or estrogen receptor-beta (ERb)-selective pro-drugs are being developed in our laboratories, the experiments will also involve (ERa)-knockout and (ERb)- knockout mice to determine the ER responsible for any effects of Q-E2. The discovery of a novel and safe ERT would improve the quality of life of hundreds of millions of perimenopausal women world-wide and thus, would have a tremendous impact on public health. Although it has not been tested experimentally, Q-E2 might be a choice for psychiatric therapy of men in the andropause as well. PUBLIC HEALTH RELEVANCE: Peri-menopausal symptoms, such as hot flushes, anxiety/depression, and sleep disturbances pose a significant public health concern world-wide. Although hormone replacement therapy, alleviates hot flushes and ease anxiety/depression and improve sleep in the majority of women, a large number of peri-menopausal women cannot take or do not want to take hormones because of their side effects. Therefore, there is a huge unmet need for better and safer therapies for menopausal symptoms. The proposal addresses this unmet need by investigating a potentially liability-free estrogen replacement therapy (ERT) utilizing animal models of hot flush, anxiety/depression, and sleep pattern. Para-quinol of estrogen (pro-drug) is converted to estrogen in brain but not in uterus and breast, and therefore, provides the foundation to develop a novel and safe, central nervous system-selective ERT.